Recent studies have revealed that western populations of little brown bats (Myotis lucifugus) in North America exhibit different hibernation behavior than their eastern counterparts. Understanding these differences is essential for assessing the risk white-nose syndrome (WNS) poses to western bat populations. We used acoustic monitoring and radiotelemetry to study the overwintering behavior of little brown bats near Juneau, Alaska during 2011–2014. Our objectives were to identify the structures they use for hibernation, measure the microclimates within those structures, and determine the timing of immergence and emergence and the length of the hibernation season. We radiotracked 10 little brown bats to underground hibernacula dispersed along two ridge systems. All hibernacula were ≤ 24.2 km from where the bats were captured. Eight bats hibernated in the “Milieu Souterrain Superficiel” (MSS), a network of air-filled underground voids between the rock fragments found in scree (talus) deposits. Two bats hibernated in holes in the soil beneath the root system of a tree or stump (rootball). At least two hibernacula in the MSS were reused in subsequent years. Average MSS and rootball temperatures were warmer and more stable than ambient temperature and were well below the optimal growth range of the fungus that causes WNS. Temperatures in the MSS dropped below freezing, but MSS temperatures increased with depth, indicating bats could avoid subfreezing temperatures by moving deeper into the MSS. Relative humidity (RH) approached 100% in the MSS and under rootballs and was more stable than ambient RH, which also was high, but dropped substantially during periods of extreme cold. Acoustic monitoring revealed that bats hibernated by late October and began emerging by the second week of April; estimates of minimum length of the hibernation season ranged from 156 to 190 days. The cold temperatures, dispersed nature of the hibernacula, and close proximity of hibernacula to summering areas may slow the spread and reduce the impacts of WNS on local populations of little brown bats.

中文翻译：

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作为蝙蝠冬眠栖息地的 Milieu Souterrain Superficiel：对白鼻综合症的影响

最近的研究表明，北美的西部小棕蝠 (Myotis lucifugus) 种群表现出与东部同类不同的冬眠行为。了解这些差异对于评估对西方蝙蝠种群构成的风险白鼻综合征 (WNS) 至关重要。我们使用声学监测和无线电遥测来研究 2011-2014 年阿拉斯加朱诺附近小棕蝙蝠的越冬行为。我们的目标是确定它们用于冬眠的结构，测量这些结构内的小气候，并确定进入和出现的时间以及冬眠季节的长度。我们用无线电追踪了 10 只棕色小蝙蝠到分布在两个山脊系统的地下冬眠区。所有冬眠区距离蝙蝠被捕获的地方≤24.2公里。八只蝙蝠在“Milieu Souterrain Superficiel”（MSS）中冬眠，这是一个充满空气的地下空隙网络，位于碎石（距骨）沉积物中发现的岩石碎片之间。两只蝙蝠在树或树桩（根球）根系下方的土壤孔中冬眠。在随后的几年中，MSS 中至少有两个冬眠植物被重复使用。平均 MSS 和根球温度比环境温度更温暖、更稳定，并且远低于导致 WNS 的真菌的最佳生长范围。MSS 中的温度降至冰点以下，但 MSS 温度随着深度的增加而升高，这表明蝙蝠可以通过深入 MSS 来避免低于冰点的温度。MSS 和根球下的相对湿度 (RH) 接近 100%，比环境 RH 更稳定，环境 RH 也很高，但在极冷时期大幅下降。声学监测显示，蝙蝠在 10 月下旬冬眠，并在 4 月的第二周开始出现；冬眠季节的最短时间估计为 156 至 190 天。寒冷的温度、冬眠的分散性质以及冬眠与避暑区的密切接近可能会减缓 WNS 的传播并减少 WNS 对当地小棕蝙蝠种群的影响。